21535421 has 8 divisors (see below), whose sum is σ = 22284288. Its totient is φ = 20790000.

The previous prime is 21535411. The next prime is 21535433. The reversal of 21535421 is 12453512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21535421 - 2⁶ = 21535357 is a prime.

It is a super-4 number, since 4×21535421⁴ (a number of 30 digits) contains 4444 as substring.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21535411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21236 + ... + 22226.

It is an arithmetic number, because the mean of its divisors is an integer number (2785536).

Almost surely, 2^21535421 is an apocalyptic number.

It is an amenable number.

21535421 is a deficient number, since it is larger than the sum of its proper divisors (748867).

21535421 is an equidigital number, since it uses as much as digits as its factorization.

21535421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1723.

The product of its digits is 1200, while the sum is 23.

The square root of 21535421 is about 4640.6272205382. The cubic root of 21535421 is about 278.2175074341.

Adding to 21535421 its reverse (12453512), we get a palindrome (33988933).

The spelling of 21535421 in words is "twenty-one million, five hundred thirty-five thousand, four hundred twenty-one".